| 摘要 |
PURPOSE:To observe the eccentric state of a medium during its revolution by receiving the reflected light of the light irradiated from an optical pickup by at least two photoelectric transducers and performing the signal processing via an adder, a subtractor and a differentiator. CONSTITUTION:A photoelectric transducer 3 uses a 2-split element, and output signals S1 and S2 are added together by an adder 4 and turned into an output signal S3. The output signal of a subtractor 5 is turned into an output signal S7. Then an output signal S4 is processed by a differentiator and turned into an output signal S6. The signal S3 is supplied to a peak detector 6 and a signal S5 is obtained. The signal S shows that the light is irradiated on a recording track. While the signal S4 is supplied to a zero-cross detector 8 to obtain the signal S7. This signal S7 is processed by a logic 10 which produces an AND of signals S7 and S5. Then a signal S9 is obtained. This signal S9 is delivered only when an irradiated position exists on the recording track. The peak of the signal S6 is detected by a peak detector 9 to obtain a signal S8. The shift direction of the recording track is discriminated by the presence or absence of the output signal S10 of a logic 11 which produces an AND of signals S5 and S8. Both signals S9 and S10 are produced by an UP/DOWN counter 12 to obtain the number of eccentric tracks of a medium.
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